Materials Literature
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Exchange interactions between hard-magnetic particles in a nonmagnetic matrix are investigated by model calculations. A Landau–Ginzburg approach is developed to describe the net exchange interactions between spheres of arbitrary diameters. Introducing cylindrical coordinates and integrating over the surfaces of the ad…
Ni 0.3 Mn x Zn 0.7- x Fe 2 O 4 samples, with x =0.1, 0.2, 0.3, 0.4, 0.5, have been prepared by the citrate precursor method and their dc resistivity, complex initial permeability, permittivity and saturation magnetization are studied. Initial increase followed by a decrease is observed in dc resistivity and saturation…
We present a model for the structure formation in nematic amorphous copolymers and simulation results for a two-dimensional (2D) implementation. The model is based on a dynamic mean-field method, which allows one to specify the polymer system on two different levels of detail. On the detailed level the nematic amorpho…
We have studied the first-order magnetic phase transition and related physical properties of MnFeP0.5As0.4Si0.1 by means of x-ray diffraction, magnetization, thermal expansion, and electrical resistance measurements. The compound crystallizes in the hexagonal structure with Fe2P-type. The temperature dependence of mag…
The films with HM=(Pr,Dy)(Fe,Co,Nb,B)5.5 and SM=Fe, FeCo were prepared by sputtering and subsequent heat treatment. The coercivity of Ti-buffered (Pr,Dy)(Fe,Co,Nb,B)5.5 single-layer film with 320 nm thickness is as large as 18.8 kOe at room temperature. X-ray diffraction results reveal that the Pr2Fe14B-type phase is…
A barium hexaferrite (BaFe12O19, magnetoplumbite structure, BaM) multilayered film, with a total thickness of 0.63 μm, was deposited on a Si substrate by stacking several 0.09 μm layers using a rf sputtering technique. Each 0.09 μm layer was ex situ annealed at 800 °C for 10 min prior to deposition of the succeeding l…
Optical second harmonic (SH) spectroscopy in the centrosymmetric antiferromagnets CoO, NiO, and KNiF3 reveals pronounced signals below the Néel temperature which couple quadratically to the magnetic order parameter. The SH process roots in resonance enhanced magnetic-dipole and electric-dipole excitations between the…
The morphological effect of Al 2 O 3 on the deactivation of V 2 O 5 /Al 2 O 3 catalyst by SO 2 for the removal of NO with NH 3 has been examined to identify the promise of alumina as a support for commercial SCR catalysts. A test program for accelerated batch-type deactivation at 400 °C and accelerated continuous deac…
We study the nonlinear current–voltage (I–V) characteristics and analyze the voltage-dependent tunneling conductance in nanoparticles of La2/3A1/3MnO3 (A=Ca, Sr). The powders were prepared by different wet-chemical routes and low calcination temperatures were used to obtain an average particle size D≈30 nm. The data a…
The change in entropy, ΔS, at the first-order magnetoelastic phase transition in Gd5(SixGe1−x)4 alloys for x⩽0.5 has been measured with a high-sensitivity differential scanning calorimeter with built-in magnetic field, H. Scaling of ΔS is achieved by changing the transition temperature, Tt, with x and H from 70 to 310…
The Stoner–Wohlfarth model has proved reasonably successful in describing the coercivities of antiferromagnetically coupled DyFe2/YFe2 hard/soft superlattices in the absence of magnetic exchange springs. In particular, the coercivity rises sharply as the net magnetic moment of the superlattice approaches zero. However…
Magnetic resonance measurements of different size NiO nanoparticles were performed at frequencies below 33 cm−1 and in the temperature range 300–500 K. The samples were earlier investigated by superconducting quantum interference device magnetometry and electron spin resonance spectrometry. The spectra were scanned by…
Mechanically alloyed Sm–Co powders and Sm12(Co,Cu,Ti)88 powders are investigated. X-ray diffraction patterns show that after annealing, structures of 2:7, 1:5, and 1:7 phases form. A room-temperature coercivity of 41 kOe was obtained in Sm2Co7 powders. Magnetic hysteresis was investigated by the method of δm curves. P…
Because of their high electrical resistivity and high magnetic permeability, nickel–zinc ferrites are among the best soft magnetic materials for high-frequency applications. In this work, a precursor of nanostructured (Ni0.5Zn0.5)Fe2O4 was obtained by a sol–gel method modified for large quantity production. Six heat-t…
A detailed study of the magnetization M(H,T) of manganites near TC is presented. Analysis, in the framework of Landau theory of phase transitions (G=G0+1/2AM2+1/4BM4+1/6CM6−MH) reveals that for La0.67Ca0.33MnO3 (TC=267 K), La0.8MnO3 (TC=250 K), and La0.60Y0.07Ca0.33MnO3 (TC=150 K) the phase transition is first-order a…
Magnetic anisotropy of sputtered epitaxial La2/3Ca1/3MnO3 (LCMO) thin films grown on top of LaAlO3 (LAO) substrates has been studied as a function of thickness. A series of films with thickness ranging from 20 to 150 nm have been prepared. LCMO films grown on LAO substrates are subjected to an in-plane biaxial compres…
We discuss the condition for delocalization of holes in N-doped ZnO, ZnS, and ZnTe. For N-doped ZnO and ZnS, we find large energy reduction due to ionic polarization and a narrow N-impurity band at the top of the valence band compared with those for N-doped ZnTe. These are due to the significant difference between the…
Formation of Ce3Fe29−x−yCoxMoy(x=0,3,6,10) compounds has been investigated by means of x-ray diffraction and magnetic measurements. It is found that the required Mo content to stabilize the 3:29 compounds decreases monotonically as Co content increases, totally different from the discovery in the Gd3(Fe1−xCox)29−yCry…
Gold nanoclusters dispersed in single crystal MgO have been prepared by ion implantation at 975 K and subsequent annealing at 1275 K for 10 h. The morphological features, size, and crystallographic orientation of the Au nanoclusters with respect to the MgO matrix, as well as the interface structure between the Au nano…
Magnetic and magnetostrictive properties of amorphous Tb-Fe thin films are investigated as functions of sputtering conditions such as the substrate thickness, input power, sputtering time, and coverage area ratio of coated thin film to substrate. The observed magnetic and magnetostrictive properties are well explained…